Large-scale surveys increasingly inquire into health-related behaviors such as sexual activity, drug use, and alcohol intake. Many of these behaviors are regarded as sensitive by potential respondents, leading sometimes to refusal to participate in the survey and sometimes to underreporting of what are regarded as undesirable behaviors. At the same time, surveys also inquire into behaviors commonly regarded as desirable e.g., condom and seat belt use and voting behavior and there are indications that such behaviors tend to be over-reported. This proposal investigates two alternative methods frequently used to reduce the threat of asking about sensitive behaviors and to increase the truthfulness of self-report: text-based computer assisted self-interviewing (text-CASI), and audio-computer assisted self-interviewing (audio CASI), comparing them with each other and with interviewer administration. We hypothesize that these methods increase the truthfulness of self-report by increasing the respondent's privacy relative to interviewer administration. Most research in this area assumes that more reporting of socially undesirable behavior, and less reporting of socially desirable behavior, is better reporting. Although this assumption is often warranted, the present study also uses validated reports of socially undesirable behavior (drunk driving), as well as validated reports of socially desirable behavior (dental visits, library card ownership and voter registration), to test hypotheses about interview mode and accuracy in reporting. The proposed research extends prior research in three ways. It examines the effect of mode of interviewing on reporting socially desirable as well as socially undesirable behavior. No one has yet examined the effect of text- or audio-CASI on the reporting of socially desirable behaviors. It examines not only differences in the frequency with which these behaviors are reported, but validates those reports against existing records. It predicts differences between text-CASI and audio-CASI based on a theory of response behavior, and tests those predictions in a controlled laboratory setting. The products of the research will be a set of findings that will guide the development and implementation of computer assisted self-interviewing (CASI) methods for surveys of behaviors and attitudes that respondents may be inclined to either over- or underreport. Given (a) the increasing interest and need for data on a variety of sensitive topics, (b) the rapid development and deployment of computer assisted methods in recent years, and (c) growing interest in extending these methods to include video as well as sound, the findings of the proposed research will have important implications for developments in this area.